<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot> </slot>
    </div>
    <div class="dots">
      <span
        class="dot"
        :class="{ active: currentPageIndex === index }"
        v-for="(item, index) in dots"
        :key="index"
      ></span>
    </div>
  </div>
</template>

<script>
import { addClass } from 'common/js/dom';
import BScroll from 'better-scroll';

export default {
  name: 'slider',
  props: {
    loop: {
      // 是否可以轮播
      type: Boolean,
      default: true,
    },
    autoplay: {
      // 循环轮播
      type: Boolean,
      default: true,
    },
    interval: {
      // 轮播间隔
      type: Number,
      default: 3000,
    },
  },
  data() {
    return {
      dots: [],
      currentPageIndex: 0,
    };
  },

  mounted() {
    setTimeout(() => {
      this._setSliderWidth();
      this._initDots();
      this._initSlider();
    }, 20);
    // window.addEventListener('resize', () => {
    //   if (!this.slider) {
    //     return;
    //   }
    //   this._setSliderWidth(true);
    //   this.slider.refresh();
    // });
  },
  methods: {
    // 计算横向滚动的快递
    _setSliderWidth(isResize) {
      this.children = this.$refs.sliderGroup.children;

      let width = 0;
      let sliderWidth = this.$refs.slider.clientWidth;
      for (let i = 0; i < this.children.length; i++) {
        let child = this.children[i];
        addClass(child, 'slider-item');

        child.style.width = sliderWidth + 'px';
        width += sliderWidth;
      }
      // Resize的时候dom渲染完成个数比实际多2个了
      if (this.loop && !isResize) {
        width += 2 * sliderWidth;
      }
      this.$refs.sliderGroup.style.width = width + 'px';
    },
    // 初始化 slider
    _initSlider() {
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true,
        scrollY: false,
        momentum: false,
        click: true,
        slide: {
          loop: this.loop,
          autoplay: this.autoplay,
          interval: this.interval,
        },
      });
      // 监听 BScroll  的 slideWillChange 事件
      this.slider.on('slideWillChange', (page) => {
        this.currentPageIndex = page.pageX;
      });
    },
    _initDots() {
      this.dots = new Array(this.children.length);
    },
  },
  beforeDestroy() {
    this.slider && this.slider.destroy();
  },
};
</script>

<style scoped lang="stylus">
@import "~common/stylus/variable"
.slider
  min-height: 1px
  .slider-group
    position: relative
    overflow: hidden
    white-space: nowrap
    .slider-item
      float: left
      box-sizing: border-box
      overflow: hidden
      text-align: center
      a
        display: block
        width: 100%
        overflow: hidden
        text-decoration: none
      img
        display: block
        width: 100%
  .dots
    position: absolute
    right: 0
    left: 0
    bottom: 12px
    text-align: center
    font-size: 0
    .dot
      display: inline-block
      margin: 0 4px
      width: 8px
      height: 8px
      border-radius: 50%
      background: $color-text-l
      &.active
        width: 20px
        border-radius: 5px
        background: $color-text-ll
</style>
